Avoid confusion with num_vertices() of graph

include/gp-bnb/partition.hpp

@@ -21,7 +21,7 @@ public:
      *  @param  Subgraph A, B or none
      *  @return Number of vertices of sg
      */
-    unsigned int num_vertices(subgraph sg);
+    unsigned int num_vertices_of(subgraph sg);
     
     /** @brief  Assigns a vertex to a subgraph
      *  @param  Vertex Id